id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc
22470	WP_Scripts: output script element only if src not empty	niallkennedy		"I was able to make async JavaScript loading work with existing !WordPress code by acting on the script_loader_src filter before the `<script>` element is output, returning an empty string. This results in an empty src attribute, creating technically invalid HTML while not immediately loading the external script. If the !WordPress code could check if a non-empty `$src` string exists before outputting I could avoid the invalid HTML nag. Attached diff only outputs the `<script src="""">` element if `$src` is not an empty string.

I'd like to be able to asynchronously load an enqueued script without needing to completely rework `WP_Scripts`. I'd like to take advantage of common handles indicating a script is set to be loaded, extra data attached to a handle, and other !WordPress script expectations while swapping out the `<script src="""">` echoed markup.

Why async? A script steps out of the way, offering progressive enhancement of the page or loading non-critical features such as stats or socal network sharing buttons. Async loading also helps prevent single points of failure in webpage loading caused by China blocking Facebook or resources hosted at Amazon Web Services going offline for a few hours.

* [http://www.stevesouders.com/blog/2012/01/13/javascript-performance/ Some info from Steve Souders] showing a 31% increase in load times.
* [https://developers.google.com/analytics/devguides/collection/gajs/ Google Analytics use case]
* [https://developers.facebook.com/docs/reference/javascript/#loading Facebook JavaScript SDK use case]"	enhancement	new	normal	Awaiting Review	General		trivial		has-patch